Tubular metallic softball (and baseball) bats are well known in the art. A familiar example is a tubular aluminum bat. Such bats have the advantage of a generally good impact response, meaning that the bat effectively transfers power to a batted ball. This effective power transfer results in ball players achieving good "slugging" distances with batted balls. An additional advantage of such aluminum bats is the improved durability over crack-prone wooden bats.
Even though today's aluminum bats perform well, there is an ever-continuing quest for bats with a better "slugging" capacity. Accordingly, one important need is to optimize the impact response of a bat. Generally speaking, impact response is best when a bat undergoes a greatest elastic deflection, before rebounding with a greatest force in the shortest amount of time. Optimization of these three factors increases the "spring" of a ball off a bat, yielding a bat with a superior power transfer and facility for "slugging."
Constraining the design of aluminum bats is the requirement that the elastic deflection not be accompanied by any plastic deformation. Plastic deflection lessens the power transfer to a ball and leaves the bat permanently dented. Thus, aluminum bat design is driven by the elastic and plastic deformation characteristics of aluminum. For example, when the tubular wall is too thin, a desirable large amount of elastic deflection is achieved, but with unwanted permanent plastic deformation. On the other hand, when the aluminum tubular wall is too thick, the bat may be too stiff to elastically deflect appreciably. In this case, the bat responds with relatively little spring, resulting in lower power transfer.
To provide for greater "spring," tubular bats using other materials, such as titanium, have been developed. Titanium is a high-strength material permitting thin bat frame walls which provide a substantial elastic deflection without plastic deformation. Such bats provide excellent spring-like response and power transfer to a batted ball. However, the material cost and difficulty of working titanium result in a high consumer cost.
The prior art also includes tubular bats using inserts. While most often inserts are used for vibration deadening purposes, U.S. Pat. No. 3,963,239 of Fujii discloses a metallic bat frame with a large-diameter impact portion receiving an insert to adjust the weight and improve the "repelling action" of the bat. Fujii teaches an insert in tight abutment within the tubular frame, so that the insert is fixed relative to the frame. The engagement is improved by forcing the insert into the tapered intermediate portion of the bat and/or by gluing the insert within the frame. The tightly-fitted Fujii insert simply acts to thicken the wall of the impact portion of the bat.
In light of the shortcomings of the prior art, it is an objective of the present invention to provide an improved bat.
It is another objective of this invention to provide a bat that increases the power transferred from the bat to a batted ball.
It is yet another objective of this invention to provide a simple construction for a tubular bat with an insert.
In accordance with a preferred embodiment of the present invention, a tubular aluminum bat frame is provided with a large-diameter impact portion, an intermediate tapering portion, and a small-diameter handle portion. A tubular insert is suspended within the impact portion by interference fits at each insert end. A first interference fit is achieved by forcing the first end of the insert into the tapering portion of the bat frame. The second interference-fit is then formed by curling the end of the impact portion over upon the second end of the insert. A gap exists along the length of the suspended insert separating the insert from the interior of the impact portion. The gap is filled with grease to facilitate relative movement between the insert and the tubular frame when a ball is batted.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.